HOLEŠINSKÝ Jan VSB - Technical University of Ostrava

Spoluautoři VODÁREK Vlastimil, STŘÍLKOVÁ Lucie, KUBOŇ Zdeněk

The paper deals with the study on creep behavior and minor phase evolution in two types of heterogeneous weld joints of P23 and P91 steels during long-term creep exposure at 550 °C. The filler material in Weld A corresponded to P91 steel and the filler metal in Weld B was similar to the chemical composition of P23 steel. The creep rupture tests on the cross-weld test pieces of both welds revealed that most failures occurred in the partly decarburized zones of P23 steel or WM23. The carbon redistribution and the minor phase evolution across the sharp P23/P91 interface were calculated using Thermocalc and Dictra computer packages. The experimental study on minor phase evolution using both EDX and SAED in TEM was in a good agreement with the computer simulations, except for M23C6 phase in P23 (WM23) steel. EBSD technique used to study on microstructure changes along the P23/P91 boundary confirmed the slowing down of the recovery/recrystallization processes in the partly decarburized zone of HAZ of the P23 steel thanks to the presence of undissolved particles of M6X and MX phases. Furthermore, the formation of Laves phase was proved in the partly decarburized zone of P23 steel. EBSD results also confirmed higher resistance of Weld A to softening processes in the partly decarburized zone of P23 steel compared to Weld B, which was in accordance with the results of creep rupture tests.